Last revised by Daniel J Bell on 29 Apr 2022

X-rays (or much more rarely, and usually historically, x-radiation or Roentgen rays) represent a form of ionizing electromagnetic radiation. They are produced by an x-ray tube, using a high voltage to accelerate the electrons produced by its cathode. The produced electrons interact with the anode, thus producing x-rays. The x-rays produced include Bremsstrahlung and the characteristic radiation for the anode element.

X-rays can interact with matter by the following:


The term x-ray as well as referring to a form of electromagnetic radiation per se, is also used to refer to the image generated, for example a chest x-ray. Although many radiologists will insist that radiograph is the correct term for this, especially in a more formal setting . X-ray is also used as a transitive verb, e.g. we x-rayed the man's chest 4.

History and etymology

X-rays were discovered by the German physicist Wilhelm Roentgen (1845-1923) in 1895. They were named x-rays or x-radiation as Rontgen did not know what they were, and he was using the symbol 'x' for an unknown quantity or thing 1. He was awarded the Nobel Prize in Physics for his groundbreaking discovery.

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